It's not that hard, but keep in mind you must be brave to answer every question you meet.
Microsoft is a very big company, but they still like clever people. The interviewer is a pretty nice guy, and the whole process is pretty relaxing.
The problem is about a graph.
Graph Problem
The following metrics were computed from 634 interview experiences for the Microsoft Software Development Engineer role in United States.
Microsoft's interview process for their Software Development Engineer roles in the United States is very selective, failing most engineers who go through it.
Candidates reported having very good feelings for Microsoft's Software Development Engineer interview process in United States.